The present invention relates to an apparatus for the monitoring of one or more threads in a sewing machine with a number of sewing heads for at least one upper thread and one lower thread and with at least one signal emitter for generating an electric signal in correspondence to the movement of the lower thread during a certain period of time.
Apparatus for the monitoring and sensing of the upper and lower threads in sewing machines with one, and in many cases several, sewing heads are exposed to relatively great mechanical stresses and have failed, as a result of shortcomings in strength and unreliability, to reach any desired degree of use. However, it is an extremely urgent demand in this art to be able to monitor the threads in order to attain as faultless seams and sewing as possible. The quicker the machines work, the greater is the need of being able to monitor the threads. Moreover, it is, in many cases desirable to be able to stop the machine automatically in the event of thread breakage. Hence, there is a great need within this art for a reliable and mechanically durable signal emitter.
The task of satisfying the above-outlined needs forms the basis of the present invention.